Smoking during pregnancy is one of the most important modifiable causes of poor pregnancy outcomes in the United States. Unfortunately, the majority of women who smoke prior to pregnancy continue to smoke during pregnancy. Even with augmented behavioral interventions, smoking cessation rates in pregnancy trials rarely exceed 20 percent. These low quit rates may be due to inadequate treatment of the physical addiction to nicotine. Indeed, medications are first-line treatment for smoking treatment in non-pregnant smokers. However, little information is available on the safety or efficacy of medications to treat pregnant smokers. This proposal will examine the utility of one first-line medication, nicotine gum, as an aid to smoking cessation during pregnancy. The specific research aims of this project are: 1. To compare smoking cessation rates and smoking reduction among pregnant smokers who are randomized to receive 2 mg nicotine gum or a matching placebo; 2. To compare nicotine gum versus placebo on surrogate measures of maternal and fetal safety (i.e., overall nicotine and tobacco exposure), and birth weight at the time of delivery; 3. To examine which subjects benefit the most from the use of nicotine gum for smoking cessation during pregnancy. Subjects will be recruited from a prenatal clinic that serves primarily a low-income, minority population. Two hundred sixty-six pregnant smokers who smoke at least 5 cigarettes per day will be randomly assigned to receive a behavioral counseling intervention and either a 6-week course of 2 mg nicotine gum or placebo for smoking cessation followed by a 6-week taper. Primary outcome measures will be 7-day point prevalence cigarette abstinence, number of cigarettes smoked per day, saliva cotinine concentrations, and measures of tobacco exposure (i.e., carbon monoxide in exhaled air, and urine anabasine and anatabine) at 6 weeks after the quit date and at 32-34 weeks gestation. Birth weight will be obtained at the time of delivery. We hypothesize that 1. Pregnant smokers who are randomized to nicotine gum will have double the quit rates, and will reduce their smoking to a greater degree than subjects randomized to placebo; 2. Nicotine gum compared to placebo will reduce maternal cotinine levels, carboxyhemoglobin levels, and urine anabasine and anatabine levels. Birth weights will be higher in the offspring of subjects randomized to nicotine gum compared to placebo and will be negatively correlated with carbon monoxide and urinary alkaloids at 32-34 weeks gestation; 3. The odds of cigarette abstinence will be increased primarily in subjects who smoke at least 15 cigarettes per day.